Sailboards operate at speed to length ratios higher than any other sailboats. Hydrodynamic drag affecting sailboat speed is comprised of two major factors, residuary resistance and frictional resistance. The residuary drag is the result of form drag and wave making drag, energy used to displace water and create the wake. The frictional resistance is the result of shearing water and is directly related to the wetted surface area. At low speeds the residuary resistance is the major portion of the total drag. The factor most effecting this drag is the water line length, longer hulls are faster for the same displacement. A hull produces a characteristics wave, the wave length being a function of speed. For a given water line length a displacement hull will reach a speed limit, hull speed, above which the drag increases exponentially. The only way to increase speed at this point is to have a planing effect to raise the hull up and reduce the volumetric displacement and the wetted surface area. In the planing regime the major contributor to drag is the frictional component, a direct function of surface area. Hydrofoils are the extreme of low surface area planing.
The early sailboards, (e.g. Darby "Popular Science" August 1965 pages 138-141) had flat bottom planing form with either a flat or pointed bow and almost no rocker. Since these early models were sailed mostly in lakes their was no need to break over waves. The next breakthrough in board design was the adaptation to a surfboard shape with longitudinal rise, rocker, in the bow and in the stern.
The fastest sailboards today are the flat bottom, wave jumpers, that take advantage of high planing forces, however this type of design can not compete in upwind sailing because of poor acceleration and poor pointing ability as a result of the flat bottom. The modern regatta boards are a trade-off between boats and surfboards and are considered to be semi displacement hull forms. The characteristics that sets these boards aside from displacement hull forms is the extreme amount of bow rocker in the semi displacement as opposed to a deep fore foot with almost no rocker in displacement hull form.
Another approach to advanced sailboard hull forms is the Wing Form (Russell U.S. Pat. No. 3,742,887) designed with a tunnel concave center to trap air, increase stability and aid in planing lift.